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Mazda CX-9 Reverse Light Bulbs Replacement Guide
How to change a burnt out reverse (back up) tail light bulb in a 2nd generation 2016 to 2021 Mazda CX-9 SUV.

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2019 CX-9 Tail Lights
Tailgate Door Cargo Area
Reverse Bulb Housing
This automotive maintenance tutorial was specifically written to assist owners of the second generation 2016, 2017, 2018, 2019, 2020 and 2021 Mazda CX-9 SUV in changing a burnt out reverse light bulb (also known as the "back-up" or "backup" bulb) in the separate tail light housing attached to the tailgate door for the cargo area.

Owners of other Mazda vehicles such as the CX-5, CX-3, CX-30, MX-30, CX-8, Mazda8 (MPV), MX-5 Miata, Mazda2 (Demio), Mazda3 (Axela), Mazda6 (Atenza) and Mazda5 (Premacy) may also find these DIY instructions to be helpful.

The compatible replacement miniature wedge base light bulb part number is W16W (also known as part # 921).

If you would like to have brighter reverse lights that will also last much longer before burning out like the traditional incandescent bulbs, install some W16W LED units.

The only tool needed to access and replace the bulbs is a flat head screwdriver or a plastic pry bar tool.

The first two steps are to open the tailgate and move to the side of the SUV with the burnt out reverse light bulb.


Plastic Access Cover
Insert Screwdriver
Pry Out Access Cover
Locate the square shaped plastic access cover on the underside of the tailgate.

There are two notches on the outer edge of the access cover.

Insert the blade of your flat head screwdriver or the small plastic pry bar tool into one of the two notches.

Gently pry out the outer edge of the access cover.

Pull out the two tabs on the inner edge of the cover from the tailgate door's plastic interior panel.

Set the access cover aside in a safe place.

Bulb Socket Exposed
Push In Release Tab
Disconnect Power Plug
Once the access cover is out of the way, you'll be able to see the reverse bulb socket.

Push in the release tab on the grey plastic electrical connector and slide it straight off the base of the bulb socket.

1/4 Turn Counterclockwise
Bulb Socket Removed
Pull Out Old Light Bulb
Rotate the base of the bulb socket 1/4 turn in the counterclockwise direction before pulling it straight out of the housing.

If the old light bulb was recently turned on, be careful when you remove it. The old bulb might still be hot enough to burn your fingers.

Pull the old light bulb straight out of the socket.

If you have trouble removing an old stubborn bulb due to rust or sand, put on a pair of protective gloves and try gently wiggling the bulb back and forth while pulling it straight out.

Try to avoid using excessive pressure on the old bulb to prevent it from breaking and possibly cutting your fingers.

Old Light Bulb Removed
Push In New Light Bulb
Insert Bulb Socket
Push a new number W16W or 921 light bulb straight into the socket.

Clean off the light bulb with a paper towel and some rubbing alcohol. If there is any grease or oil on the incandescent light bulb, it could cause a hot spot and reduce the lifespan of the bulb.

If you'd like to have brighter reverse lights, install some compatible replacement W16W LED bulbs.

Re-insert the bulb socket into the housing and rotate it 1/4 turn in the clockwise direction to secure it in place.

1/4 Turn Clockwise - Lock
Push In Power Plug
Insert Tabs Inner Edge
Push the electrical connector straight on to the base of the bulb socket.

You should feel or hear the power plug "click" securely into place.

Line up the plastic access cover with the two tabs on the inner edge.

Re-insert the tabs on the inner edge first.

Pop In Outer Edge
Access Cover Secured
Test New Reverse Bulb
Then gently pop in the retaining clips on the outer edge of the access cover.

Close the tailgate to complete the job.

To test the new light bulbs, have your assistant step on the brake pedal and shift the transmission into "R" (Reverse).

Tip - If you installed an LED bulb and it doesn't work, try removing it from the socket, rotating it 180 degrees and pushing it back into the socket. Some LED bulbs are "polarized" and will only work when the "+" positive and "-" negative electrical contacts in the correct orientation.

Don't forget to write down the bulb change in your vehicle's service records.

For more, please check out all of the 2016-2021 Mazda CX-9 DIY Repair & Maintenance Guides.

If you found this guide to be helpful, please consider making a small donation by clicking on the "Donate" button located to the right of this paragraph. Thank you!
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